EFFECTS OF HIGH-TEMPERATURE ANNEALING ON THE OPTICAL-ABSORPTION OF CA-YIG FILMS

The effect of high-temperature annealing on the optical properties of a calcium doped yttrium iron garnet (Ca:YIG) film were studied. The op tical absorption was examined for a film of Ca-0.18:YIG reduced in an atmosphere of N-2 at temperatures above 900 degrees C. During the anne aling, the optical absorption initially decreased below the as-grown v alue as expected, but subsequently increased to a value greater than t hat for the as-grown him as the annealing temperatures were increased. The changes observed in the optical absorption are believed to be due to the. introduction of oxygen vacancies in the him as a result of th e annealing. Initially the added oxygen vacancies simply compensate th e Ca2+, while successive annealings introduce excess vacancies which l ead to a new absorption mechanism. The results of this study and the e xpected mechanism for the effect are reported. (C) 1996 American Insti tute of Physics.